Climate change is happening, it is a fact.
There is now overwhelming scientific consensus that the atmospheric build-up of greenhouse gases is causing climate change. However, despite repeated warnings over the past 40 years, Australian activist Paul Gilding has pointed out that we have not managed to do very much at all to mitigate climate change. In fact we have barely started to take any real action.
The Consensus Project
In a review of 12,464 scientific papers on climate change published between 1991-2011, the authors found that 97% of the papers agreed with the consensus position of anthropogenic (human-caused) climate change.
In a pivotal article published in Science from 2004, Naomi Oreskes reviewed 928 scientific papers from leading journals and found that not a single paper disagreed with the consensus opinion that anthropogenic (human caused) greenhouse gas emissions is leading to climate change.
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is regularly conducting systematic reviews of the scientific evidence base and declared in 2013 that “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”
For the latest evidence on climate change, Dr. James Hansen, a leading climatologist at NASA and Columbia University, regularly updates key graphs showing that climate change is progressing. An excellent TED presentation by Dr. Hansen can be found here.
The web site Skeptical Science has done an excellent job at collecting and debunking common arguments advocated by climate change skeptics.
Greenhouse gas build-up
Climate change is driven by the atmospheric build-up of greenhouse gases
Carbon dioxide is the most common of all greenhouse gasses. It accounts for over 77% of all emissions. Carbon dioxide is one of six greenhouse gases that are governed by the Kyoto Protocol. The largest emission sources of greenhouse gases on a global level are energy supply followed by industry and forestry.
From measurements on ice cores extracted from Antarctica, scientists have been able to estimate the atmospheric concentration of carbon dioxide during the past 400,000 years. Seen in this extraordinary long perspective, the atmospheric concentration of carbon dioxide has fluctuated from lows of around 180-200 parts per million (ppm) during ice ages to highs of between 270-300 during so called interglacial warm periods similar to our current age. In comparison, the 2012 mean carbon dioxide concentration was 394 ppm as measured at Mauna Loa, Hawaii where measurements have been taken continuously since 1959 when the initial value recorded was 316. This means an increase of 78 ppm, or 25%, just since 1959.
Chart with the greenhouse gases and % of emissions [please make pie chart]
• Carbon dioxide (C02) – 77%
• Methane (CH4) – 14%
• Nitrous oxide (N20) – 8 %
• Hydrofluorocarbons (HFCs) – less than 0.1%
• Perfluorocarbons (PFCs) – less than 0.1%
• Sulphur hexafluoride (SF6) – less than 0.1%
Data source available here.
As greenhouse gases remain in the atmosphere for a significant period of time, we are dealing with a “stock-flow” problem where annual greenhouse gas “flow” emissions contribute to the total “stock” in the atmosphere. The implication is that there is a time-lag from the point in time when a reduction is made to annual emissions until cumulative greenhouse gases are reduced.
Chart with emission sources and % of greenhouse gases [please make pie chart]
• Energy supply (25.9%)
• Industry - 19.4%
• Forestry - 17.4%
• Agriculture - 13.5%
• Transportation- 13.1%
• Buildings - 7.9%
• Waste/waste water - 2.8%
Data source available here.
Developing countries suffer most
Developing countries will suffer the most from the consequences of climate change
Despite having contributed the least to climate change, the consultancy Maplecroft has forecasted that developing countries in Asia, Africa and Latin America will suffer the most serious consequences as a result of climate change. We are no longer just talking about small island states like the Maldives but about serious impact on major countries in South Asia, Southeast Asia, Africa and Latin America
A common measurement to calculate the “carbon footprint” of products, individuals or companies.
It is common practice to convert greenhouse gases to carbon dioxide equivalents. This common measurement is often abbreviated as “CO2e” or “CDE” as in Metric Tons of Carbon Dioxide Equivalents (MTCDE).
Read more about greenhouse gas conversions (clickable link)
To convert greenhouse gases to carbon dioxide equivalents there is a conversion method known as 100-year Global Warming Potentials (GWP). Using carbon dioxide as the benchmark, a unit of methane has 21 times the GWP while a unit of nitrous oxide has 310 times the GWP. These conversion factors make it possible to compute overall greenhouse gas emissions using a common yardstick known as carbon dioxide equivalents, often abbreviated as “CO2e” or “CDE” as in Metric Tons of Carbon Dioxide Equivalents (MTCDE). This is the currency commonly used when discussing the “carbon footprint” of a product, individual or company.
Carbon dioxide is not the same as carbon given that the former molecule contains two oxygen atoms in addition to one carbon atom. Carbon has an atomic mass of 12 while oxygen has an atomic mass of 16. As carbon dioxide consists of one carbon atom and two oxygen atoms, the mass of carbon dioxide is equal to 12 + 2*16 = 44. This is in contrast to a mass of just 12 for a lone carbon atom. This means that one tonne of carbon dioxide contains 0.27 tons of carbon. Or conversely that one tonne of carbon equals 3.67 tons of carbon dioxide.